The present invention relates to an ink-jet recording head, in which a portion of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets is constituted of a vibration plate, a piezoelectric element is provided via this vibration plate, and ink droplets are ejected by displacement of the piezoelectric element. Furthermore, the present invention relates to a manufacturing method of the same and an ink-jet recording apparatus.
As an ink-jet recording head having a structure that a part of a pressure generating chamber communicating with a nozzle orifice for ejecting ink droplets is constructed by a vibration plate, and a piezoelectric element allows the vibration plate to be deformed to pressurize ink in the pressure generating chamber, thus ejecting ink droplets from the nozzle orifice, two sorts of the ink-jet recording heads have been put into practical use. Specifically, one uses a piezoelectric actuator in a longitudinal vibration mode in which the actuator stretches and contracts in the axial direction of the piezoelectric element, and the other uses a piezoelectric element in a flexural vibration mode.
While the former is capable of changing the volume of the pressure generating chamber by allowing an end face of the piezoelectric element to thrust the vibration plate and manufacturing a head suitable for high density printing, the former has been involved in a problem that a troublesome step for cutting the piezoelectric element to be comb-tooth shaped so as to be coincident with an arrangement pitch of the nozzle orifice must be performed as well as an operation to position the cut piezoelectric element in the pressure generating chamber and fix it thereto, thus making manufacturing steps complicated.
On the other hand, while the latter can fix the piezoelectric element to the vibration plate with a relatively simple step for adhering a green sheet of piezoelectric material to the vibration plate so as to fit it to the shape of the pressure generating chamber and sintering them. However, a certain size of vibration plate is required due to the usage of flexural vibration, thus there is a problem that high density array of the piezoelectric elements is difficult.
On the other hand, to solve the disadvantages of the recording head of the latter, as disclosed in Japanese Patent Laid-Open No. 50-286131, a recording head is proposed, in which a piezoelectric material layer having an even thickness is formed over the entire surface of a vibration plate by a film growth method, and this piezoelectric material layer is cut by a lithography method so that each piece of the layer fits to the shape of respective pressure generating chambers, thus forming piezoelectric elements independently for the respective pressure generating chambers.
According to this recording head, the operation to adhere the piezoelectric element to the vibration plate is unnecessary, and hence not only the piezoelectric element can be fixed to the vibration plate by the lithography method that is precise and simple, but also the thickness of the piezoelectric element can be made small, thus enabling a high speed drive.
However, in the case where the piezoelectric element is formed by sputtering the piezoelectric material, when the piezoelectric element is driven at a voltage approximately equal to that for driving one formed by sintering the green sheet, a higher electric field is applied thereto as the thickness of the piezoelectric element becomes smaller. When the piezoelectric element absorbs humidity in the air, the leak current between driving electrodes is apt to increase, leading to a dielectric breakdown.
The present invention was invented from the viewpoint of the foregoing circumstances, and the object of the present invention is to provide an ink-jet recording head which prevents operational malfunction of the piezoelectric element due to external environments around such as humidity, a method of manufacturing the same, and an ink-jet recording apparatus.
A first aspect of the present invention is an ink-jet recording head which comprises a passage-forming substrate in which a pressure generating chamber communicating with a nozzle orifice is partitioned by a plurality of compartment walls, and a piezoelectric element provided on one plane side of the passage-forming substrate and causing a change in pressure in the pressure generating chamber. The ink-jet recording head comprising: a joint member jointed to a piezoelectric element side of said passage-forming substrate, said joint member having piezoelectric element holding portion securing a space having a volume so as not to disturb movement of said piezoelectric element and at least one communication hole allowing said piezoelectric element holding portion to communicate with the outside, wherein a sealing member made of resin is filled in said communication hole, so that said piezoelectric element holding portion is hermetically sealing.
In the first aspect of the present invention, the piezoelectric element can be hermetically sealed in the piezoelectric element holding portion relatively easily, and the ink-jet recording head can be realized, which is capable of preventing operational malfunctions of the piezoelectric element owing to external environments.
A second aspect of the present invention according to the first aspect is the ink-jet recording head in which the piezoelectric element holding portion is sealed under air pressure lower than atmospheric pressure.
In the second aspect of the present invention, since the sealing member for sealing the communication hole is partially pulled into the communication hole, the piezoelectric element holding portion can be hermetically sealed more surely.
A third aspect of the present invention according to the second aspect is the ink-jet recording head in which a part of the communication hole is constituted by a groove portion formed on a joint plane of the joint member and the passage-forming substrate.
In the third aspect of the present invention, by adjusting the shape and length of the groove portion, a quantity of the sealing member pulled into the communication hole is controlled.
A fourth aspect of the present invention according to any one of the first to third aspects is the ink-jet recording head in which a total length x of the communication hole is a length satisfying the relation expressed by the following equation (1) represented by a flow path resistance R per a unit length of the communication hole, an injection pressure P when the sealing member is injected into the communication hole, an orifice area S of the communication hole and a time t for which the sealing member is cured.                     x         greater than                                             2              xc3x97              P              xc3x97              t                                                          R              xc3x97              S                                                          (        1        )            
In the fourth aspect of the present invention, since the length of the communication hole can be made relatively short so that the sealing member does not enter the piezoelectric element holding portion, an area of the joint member can be controlled to be small, and cost can be reduced.
A fifth aspect of the present invention according to any one of the first to fourth aspects is the ink-jet recording head having a resistance portion in a part of the communication hole in the length direction thereof, the resistance portion showing a flow path resistance higher than that of other portions of the communication hole.
In the fifth aspect of the present invention, the resistance portion can surely prevent the sealing member from entering the piezoelectric element holding portion.
A sixth aspect of the present invention according to the fifth aspect is the ink-jet recording head in which the resistance portion of the communication hole has a narrower cross section than those of other portions of the communication hole.
In the sixth aspect of the present invention, by setting the cross section of the resistance portion to be narrower than those of other portions of the communication hole, the flow path resistance of the resistance portion can be made larger than those of other portions of the communication hole relatively easily.
A seventh aspect of the present invention according to any one of the fifth and sixth aspects is the ink-jet recording head in which the resistance portion is provided at a position of the communication hole which the sealing member enters.
In the seventh aspect of the present invention, it is possible to surely prevent the sealing member from entering the piezoelectric element holding portion.
An eighth aspect of the present invention according to any one of the third to seventh aspects is the ink-jet recording head in which the communication hole meanders on a joint plane in a direction to connect the piezoelectric element holding portion and the communication hole for allowing the piezoelectric element holding portion to communicate with the outside.
In the eighth aspect of the present invention, the communication hole having a desired length can be formed in a relatively narrow area.
A ninth aspect of the present invention according to any one of the first to eighth aspects is the ink-jet recording head in which dry fluid is filled in the piezoelectric element holding portion.
In the ninth aspect of the present invention, since the piezoelectric element is held in a dry fluid atmosphere, operational malfunctions of the piezoelectric element owing to external environments can be surely prevented.
A tenth aspect of the present invention according to the ninth aspect is the ink-jet recording head in which the dry fluid is inert gas.
In the tenth aspect of the present invention, the piezoelectric element is held in an atmosphere of the inert gas and isolated from external environments.
An eleventh aspect of the present invention according to the ninth aspect is the ink-jet recording head in which the dry fluid contains oxidized gas.
In the eleventh aspect of the present invention, deterioration of a piezoelectric layer principally made of oxide can be prevented.
A twelfth aspect of the present invention according to any one of the first to eleventh aspects is the ink-jet recording head in which a driving IC for driving the piezoelectric element is loaded on the joint member, and a protection member made of resin provided so as to cover the driving IC also performs a role as the sealing member.
In the twelfth aspect of the present invention, since the protection member also performs the role as the sealing member, manufacturing cost can be reduced.
A thirteenth aspect of the present invention according any one of the first to twelfth aspects is the ink-jet recording head in which the pressure generating chamber is formed in the single crystal silicon substrate by anisotropic etching, and each layer forming the piezoelectric element is formed by a film growth method and a lithography method.
In the thirteenth aspect of the present invention, the ink-jet recording head in which a nozzle orifice is provided with a high density can be mass-produced relatively easily.
A fourteenth aspect of the present invention is an ink-jet recording apparatus which comprises the ink-jet recording head according to any one of the first to thirteenth aspects.
In the fourteenth aspect of the present invention, the ink-jet recording apparatus, improving reliability of the head can be achieved.
A fifteenth aspect of the present invention is a method of manufacturing an ink-jet recording head which comprises: a passage-forming substrate in which a pressure generating chamber communicating with a nozzle orifice is partitioned by a plurality of compartment walls; and a piezoelectric element provided on one plane side of the passage-forming substrate and causing a change in pressure in the pressure generating chamber. The method comprises: a first step for adhering a piezoelectric side of said passage-forming substrate and joint member to each other, so that a joint body is formed; said joint member having a piezoelectric element holding portion securing a space having a volume on the piezoelectric element side of said passage-forming substrate so as not to disturb the motion of the piezoelectric element and a communicating hole allowing the piezoelectric element holding portion to communicate with the outside; a second step for dropping uncured resin at least onto the communication hole of the joint member constituting the joint body; a third step for disposing the joint body in a predetermined sealed space and decompressing the sealed space; and a fourth step for restoring the sealed space to a normal pressure and curing the uncured resin.
In the fifteenth aspect of the present invention, the communication hole can be sealed by the resin relatively easily and surely, and the piezoelectric element holding portion can surely be hermeticall sealed.
A sixteenth aspect of the present invention according to the fifteenth aspect is the method of manufacturing an ink-jet recording head, the method further comprising: a step for replacing the air in the piezoelectric element holding portion with dry fluid prior to the second step.
In the sixteenth aspect of the present invention, since the dry fluid is filled in the piezoelectric element holding portion, the piezoelectric element is held in the dry fluid atmosphere, and operational malfunctions of the piezoelectric element owing to external environments can be prevented.
A seventeenth aspect of the present invention according to the sixteenth aspect is the method of manufacturing an ink-jet recording head, wherein the replacing step includes a step for disposing the joint body in a predetermined sealed space filled with the dry fluid and decompressing the sealed space, and a step for introducing the dry fluid into the sealed space and restoring the sealed space to a normal pressure.
In the seventeenth aspect of the present invention, the dry fluid can be filled in the piezoelectric element holding portion relatively easily and surely.
An eighteenth aspect of the present invention according to any one of the fifteenth to seventeenth aspects is the method of manufacturing an ink-jet recording head, wherein, in the second step, the uncured resin is provided so as to cover the drive circuit for driving the piezoelectric element provided on the joint member.
In the eighteenth aspect of the present invention, the piezoelectric element holding portion can be sealed by resin, and the drive circuit can be protected. In addition, the manufacturing steps can be simplified.